System and methods for casting physical tooth model

ABSTRACT

A casting chamber for casting a physical tooth model representing a patient&#39;s tooth includes a chamber body and a lid. The chamber body includes a cavity adapted to hold a negative impression of the patient&#39;s tooth and to receive a cast material, wherein the negative impression and the chamber body are registered by a registration unit. The chamber lid is configured to seal the cast material in the casting chamber to permit the casting material to solidify in the casting chamber to form a physical tooth model representing the patient&#39;s tooth.

CROSS-REFERENCES TO RELATED INVENTIONS

The present invention is related to concurrently filed and commonlyassigned U.S. patent application, titled “A base for physical dentalarch model” by Huafeng Wen, concurrently filed and commonly assignedU.S. patent application, titled “Accurately producing a base forphysical dental arch model” by Huafeng Wen, concurrently filed andcommonly assigned U.S. patent application, titled “Fabricating a basecompatible with physical dental tooth models” by Huafeng Wen,concurrently filed and commonly assigned U.S. patent application, titled“Producing non-interfering tooth models on a base” by Huafeng Wen,concurrently filed and commonly assigned U.S. patent application, titled“Producing a base for accurately receiving dental tooth models” byHuafeng Wen, and concurrently filed and commonly assigned U.S. patentapplication, titled “Producing accurate base for dental arch model” byHuafeng Wen.

The present invention is also related to U.S. patent application, titled“Method and apparatus for manufacturing and constructing a physicaldental arch model” by Huafeng Wen, Nov. 1, 2004, U.S. patentapplication, titled “Method and apparatus for manufacturing andconstructing a dental aligner” by Huafeng Wen, Nov. 1, 2004, U.S. patentapplication, titled “Producing an adjustable physical dental arch model”by Huafeng Wen, Nov. 1, 2004, and U.S. patent application, titled“Producing a base for physical dental arch model” by Huafeng Wen, Nov.1, 2004. The disclosure of these related applications are incorporatedherein by reference.

TECHNICAL FIELD

This application generally relates to the field of dental care, and moreparticularly to a system and a method for manufacturing and constructinga physical dental arch model.

BACKGROUND

Orthodontics is the practice of manipulating a patient's teeth toprovide better function and appearance. In general, brackets are bondedto a patient's teeth and coupled together with an arched wire. Thecombination of the brackets and wire provide a force on the teethcausing them to move. Once the teeth have moved to a desired locationand are held in a place for a certain period of time, the body adaptsbone and tissue to maintain the teeth in the desired location. Tofurther assist in retaining the teeth in the desired location, a patientmay be fitted with a retainer.

To achieve tooth movement, orthodontists utilize their expertise tofirst determine a three-dimensional mental image of the patient'sphysical orthodontic structure and a three-dimensional mental image of adesired physical orthodontic structure for the patient, which may beassisted through the use of x-rays and/or models. Based on these mentalimages, the orthodontist further relies on his/her expertise to placethe brackets and/or bands on the teeth and to manually bend (i.e.,shape) wire, such that a force is asserted on the teeth to repositionthe teeth into the desired physical orthodontic structure. As the teethmove towards the desired location, the orthodontist makes continualjudgments as to the progress of the treatment, the next step in thetreatment (e.g., new bend in the wire, reposition or replace brackets,is head gear required, etc.), and the success of the previous step.

In general, the orthodontist makes manual adjustments to the wire and/orreplaces or repositions brackets based on his or her expert opinion.Unfortunately, in the oral environment, it is impossible for a humanbeing to accurately develop a visual three-dimensional image of anorthodontic structure due to the limitations of human sight and thephysical structure of a human mouth. In addition, it is humanlyimpossible to accurately estimate three-dimensional wire bends (with anaccuracy within a few degrees) and to manually apply such bends to awire. Further, it is humanly impossible to determine an ideal bracketlocation to achieve the desired orthodontic structure based on themental images. It is also extremely difficult to manually place bracketsin what is estimated to be the ideal location. Accordingly, orthodontictreatment is an iterative process requiring multiple wire changes, withthe process success and speed being very much dependent on theorthodontist's motor skills and diagnostic expertise. As a result ofmultiple wire changes, patient discomfort is increased as well as thecost. As one would expect, the quality of care varies greatly fromorthodontist to orthodontist as does the time to treat a patient.

As described, the practice of orthodontic is very much an art, relyingon the expert opinions and judgments of the orthodontist. In an effortto shift the practice of orthodontic from an art to a science, manyinnovations have been developed. For example, U.S. Pat. No. 5,518,397issued to Andreiko, et. al. provides a method of forming an orthodonticbrace. Such a method includes obtaining a model of the teeth of apatient's mouth and a prescription of desired positioning of such teeth.The contour of the teeth of the patient's mouth is determined, from themodel. Calculations of the contour and the desired positioning of thepatient's teeth are then made to determine the geometry (e.g., groovesor slots) to be provided. Custom brackets including a special geometryare then created for receiving an arch wire to form an orthodontic bracesystem. Such geometry is intended to provide for the disposition of thearched wire on the bracket in a progressive curvature in a horizontalplane and a substantially linear configuration in a vertical plane. Thegeometry of the brackets is altered, (e.g., by cutting grooves into thebrackets at individual positions and angles and with particular depth)in accordance with such calculations of the bracket geometry. In such asystem, the brackets are customized to provide three-dimensionalmovement of the teeth, once the wire, which has a two dimensional shape(i.e., linear shape in the vertical plane and curvature in thehorizontal plane), is applied to the brackets.

Other innovations relating to bracket and bracket placements have alsobeen patented. For example, such patent innovations are disclosed inU.S. Pat. No. 5,618,716 entitled “Orthodontic Bracket and Ligature” amethod of ligating arch wires to brackets, U.S. Pat. No. 5,011,405“Entitled Method for Determining Orthodontic Bracket Placement,” U.S.Pat. No. 5,395,238 entitled “Method of Forming Orthodontic Brace,” andU.S. Pat. No. 5,533,895 entitled “Orthodontic Appliance and GroupStandardize Brackets therefore and methods of making, assembling andusing appliance to straighten teeth”.

Kuroda et al. (1996) Am. J. Orthodontics 110: 365-369 describes a methodfor laser scanning a plaster dental cast to produce a digital image ofthe cast. See also U.S. Pat. No. 5,605,459. U.S. Pat. Nos. 5,533,895;5,474,448; 5,454,717; 5,447,432; 5,431,562; 5,395,238; 5,368,478; and5,139,419, assigned to Ormco Corporation, describe methods formanipulating digital images of teeth for designing orthodonticappliances.

U.S. Pat. No. 5,011,405 describes a method for digitally imaging a toothand determining optimum bracket positioning for orthodontic treatment.Laser scanning of a molded tooth to produce a three-dimensional model isdescribed in U.S. Pat. No. 5,338,198. U.S. Pat. No. 5,452,219 describesa method for laser scanning a tooth model and milling a tooth mold.Digital computer manipulation of tooth contours is described in U.S.Pat. Nos. 5,607,305 and 5,587,912. Computerized digital imaging of thearch is described in U.S. Pat. Nos. 5,342,202 and 5,340,309.

Other patents of interest include U.S. Pat. Nos. 5,549,476; 5,382,164;5,273,429; 4,936,862; 3,860,803; 3,660,900; 5,645,421; 5,055,039;4,798,534; 4,856,991; 5,035,613; 5,059,118; 5,186,623; and 4,755,139.

The key to efficiency in treatment and maximum quality in results is arealistic simulation of the treatment process. Today's orthodontistshave the possibility of taking plaster models of the upper and lowerarch, cutting the model into single tooth models and sticking thesetooth models into a wax bed, lining them up in the desired position, theso-called set-up. This approach allows for reaching a perfect occlusionwithout any guessing. The next step is to bond a bracket at every toothmodel. This would tell the orthodontist the geometry of the wire to runthrough the bracket slots to receive exactly this result. The next stepinvolves the transfer of the bracket position to the originalmalocclusion model. To make sure that the brackets will be bonded atexactly this position at the real patient's teeth, small templates forevery tooth would have to be fabricated that fit over the bracket and arelevant part of the tooth and allow for reliable placement of thebracket on the patient's teeth. To increase efficiency of the bondingprocess, another option would be to place each single bracket onto amodel of the malocclusion and then fabricate one single transfer trayper arch that covers all brackets and relevant portions of every tooth.Using such a transfer tray guarantees a very quick and yet precisebonding using indirect bonding.

U.S. Pat. No. 5,431,562 to Andreiko et al. describes a computerized,appliance-driven approach to orthodontics. In this method, first certainshape information of teeth is acquired. A uniplanar target arcform iscalculated from the shape information. The shape of customized bracketslots, the bracket base, and the shape of the orthodontic archwire, arecalculated in accordance with a mathematically-derived target archform.The goal of the Andreiko et al. method is to give more predictability,standardization, and certainty to orthodontics by replacing the humanelement in orthodontic appliance design with a deterministic,mathematical computation of a target archform and appliance design.Hence the '562 patent teaches away from an interactive, computer-basedsystem in which the orthodontist remains fully involved in patientdiagnosis, appliance design, and treatment planning and monitoring.

More recently, Align Technologies began offering transparent, removablealigning devices as a new treatment modality in orthodontics. In thissystem, an impression model of the dentition of the patient is obtainedby the orthodontist and shipped to a remote appliance manufacturingcenter, where it is scanned with a CT scanner. A computer model of thedentition in a target situation is generated at the appliancemanufacturing center and made available for viewing to the orthodontistover the Internet. The orthodontist indicates changes they wish to maketo individual tooth positions. Later, another virtual model is providedover the Internet and the orthodontist reviews the revised model, andindicates any further changes. After several such iterations, the targetsituation is agreed upon. A series of removable aligning devices orshells are manufactured and delivered to the orthodontist. The shells,in theory, will move the patient's teeth to the desired or targetposition.

U.S. Pat. No. 6,699,037 Align Technologies describes an improved methodsand systems for repositioning teeth from an initial tooth arrangement toa final tooth arrangement. Repositioning is accomplished with a systemcomprising a series of appliances configured to receive the teeth in acavity and incrementally reposition individual teeth in a series of atleast three successive steps, usually including at least four successivesteps, often including at least ten steps, sometimes including at leasttwenty-five steps, and occasionally including forty or more steps. Mostoften, the methods and systems will reposition teeth in from ten totwenty-five successive steps, although complex cases involving many ofthe patient's teeth may take forty or more steps. The successive use ofa number of such appliances permits each appliance to be configured tomove individual teeth in small increments, typically less than 2 mm,preferably less than 1 mm, and more preferably less than 0.5 mm. Theselimits refer to the maximum linear translation of any point on a toothas a result of using a single appliance. The movements provided bysuccessive appliances, of course, will usually not be the same for anyparticular tooth. Thus, one point on a tooth may be moved by aparticular distance as a result of the use of one appliance andthereafter moved by a different distance and/or in a different directionby a later appliance.

The individual appliances will preferably include a polymeric shellhaving the teeth-receiving cavity formed therein, typically by moldingas described below. Each individual appliance will be configured so thatits tooth-receiving cavity has a geometry corresponding to anintermediate or end tooth arrangement intended for that appliance. Thatis, when an appliance is first worn by the patient, certain of the teethwill be misaligned relative to an undeformed geometry of the appliancecavity. The appliance, however, is sufficiently resilient to accommodateor conform to the misaligned teeth, and will apply sufficient resilientforce against such misaligned teeth in order to reposition the teeth tothe intermediate or end arrangement desired for that treatment step.

The fabrication of aligners by Align Technologies utilizes stereolithography process as disclosed in U.S. Pat. Nos. 6,471,511 and6,682,346. Several drawbacks exist however with the stereo lithographyprocess. The materials used by stereo lithography process may be toxicand harmful to human health. Stereo lithography process builds thealigner mold layer by layer causing the resulting aligners to have astairmaster like spacing between the layers and such spacing has atendency house germs and bacteria while it is worn by a patient.Furthermore, stereo lithography process used by Align Technology alsorequires a different aligner mold at each stage of the treatment, whichproduces waste and is environmental unfriendly.

The practice of orthodontics and other dental treatments includingpreparation of a denture can benefit from a physical dental arch modelthat is representative of the dentition and the alveolar ridge of apatient to be orthodontically treated. The physical dental arch model,also referred as a physical dental arch model, is often prepared basedon an impression model. The physical dental arch model is generallyprepared by cutting and arranging individual teeth on the alveolar ridgeof the impression model. With this physical dental arch model soprepared, not only is a final goal for the dental treatment made clear,but also the occlusal condition between the maxillary and the mandibulardentitions can be ascertained specifically.

Also, the patient when the physical dental arch model is presented canvisually ascertain the possible final result of orthodontic treatment heor she will receive and, therefore, the physical dental arch model is aconvenient tool in terms of psychological aspects of the patient.

Making a model for a whole or a large portion of an arch is moredifficult than making one tooth abutment for implant purposes. Singleteeth do not have concavities and complexities as in the inter-proximalareas of teeth in an arch. Some prior art making the physical dentalarch model is carried out manually, involving not only a substantialamount of labor required, but also a substantial amount of time. It isalso difficult to machine an accurate arch model because of the variouscomplex shapes and the complex features such as inter-proximal areas,wedges between teeth, among others, in an arch.

SUMMARY OF THE INVENTION

In one aspect, the present system relates to a casting chamber forcasting a physical tooth model representing a patient's tooth,comprising:

a chamber body having a cavity adapted to hold the negative impressionof the patient's tooth and to receive a cast material; and

a chamber lid configured to seal the cast material in the castingchamber to permit the casting material to solidify in the castingchamber thereby forming a physical tooth model representing thepatient's tooth.

In another aspect, the present system relates to a casting chamber forcasting a physical tooth model representing a patient's tooth,comprising:

a chamber body having a cavity adapted to hold the negative impressionof the patient's tooth and to receive a cast material and chamber wallssurrounding the cavity, wherein the negative impression and the chamberbody are registered by a registration unit; and

a chamber lid configured to seal the cast material in the castingchamber to permit the casting material to solidify in the castingchamber thereby forming a physical tooth model representing thepatient's tooth.

In yet another aspect, the present system relates to a method forproducing a physical tooth model, comprising:

holding a negative impression of a patient's tooth in a casting chamberby a registration unit;

pouring a cast material over the negative impression of the patient'stooth; and

solidifying the cast material to produce the physical tooth model.

Embodiments may include one or more of the following advantages. Anadvantage of the present system is that the physical tooth models can beproduced with simple, inexpensive and reliable methods and system. Thephysical tooth models are molded to the correct shape including featuresto allow them to be inserted, attached, or plugged to a dental base. Thephysical tooth models can be pre-fabricated having standard registrationand attaching features for assembling. The physical tooth models can beautomatically assembled onto a base by a robotic arm under computercontrol. The manufacturable components can be attached to a base. Theassembled physical dental arch model specifically corresponds to thepatient's arch. There is no need for complex and costly units such asmicro-actuators for adjusting multiple degrees of freedom for each toothmodel. The described methods and system is simple to make and easy touse.

The physical dental arch model obtained by the disclosed system andmethods can be used for various dental applications such as dentalcrown, dental bridge, aligner fabrication, biometrics, and teethwhitening. The arch model can be assembled from segmented manufacturablecomponents that can be individually manufactured by automated, precisenumerical manufacturing techniques.

Yet another advantageous feature of the disclosed system and methods isthat the physical tooth models in the physical dental arch model can beeasily separated, repaired or replaced, and reassembled after theassembly without the replacement of the whole arch model.

The details of one or more embodiments are set forth in the accompanyingdrawing and in the description below. Other features, objects, andadvantages of the system will become apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawing, which are incorporated in and form a part ofthis specification, illustrate embodiments of the system and, togetherwith the description, serve to explain the principles of the system:

FIG. 1 is a flow chart for producing a physical dental arch model inaccordance with the present system.

FIG. 2 illustrates a tooth model and a base respectively comprisingcomplimentary features for assembling the tooth model with the base.

FIG. 3 illustrates fixing a stud to a tooth model comprising a femalesocket to produce a tooth model having a protruded stud.

FIGS. 4 illustrate a tooth model comprising two pins that allow thetooth model to be plugged into two corresponding holes in a base.

FIGS. 5 illustrate a tooth model comprising a protruded pin that allowsthe tooth model to be plugged into a hole in a base.

FIG. 6 illustrates cone shaped studs protruded out of the bottom of atooth model.

FIG. 7 illustrates exemplified shapes for the studs at the bottom of atooth model.

FIG. 8A illustrates an example of a base comprising a plurality offemale sockets for receiving a plurality of tooth models for forming aphysical dental arch model.

FIG. 8B illustrates another example of a base comprising a plurality offemale sockets for receiving a plurality of tooth models for forming aphysical dental arch model.

FIG. 9 illustrates a tooth model that can be assembled to the base inFIGS. 8A and 8B.

FIG. 10 illustrates an exploded top perspective view of a castingchamber, a chamber lid, and a base for casting a physical tooth model.

FIG. 11 illustrates an exploded bottom perspective view of a castingchamber, a chamber lid, and a base for casting a physical tooth model.

DESCRIPTION OF INVENTION

Major operations in producing a physical dental arch model areillustrated in FIG. 1. The process generally includes the followingsteps. First individual tooth model is created in step 110. Anindividual tooth model is a physical model that can be part of aphysical tooth arch model, which can be used in various dentalapplications. Registration features are next added to the individualtooth model to allow them to be attached to each other or a base in step120. A base is designed for receiving the tooth model in step 130. Thetooth model positions in a tooth arch model are next determined in step140. A base is fabricated in step 150. The base includes features forreceiving the individual tooth model. The tooth models are finallyattached to the base at the predetermined positions using thepre-designed features in step 160.

Details of process in FIG. 1 are now described. Individual tooth modelscan be obtained in step 110 in a number of different methods. The toothmodel can be created by casting. A negative impression is first madefrom a patient's arch or a patient's tooth using for example PVS. Thenegative impression of the patient's arch is placed in a speciallydesigned chamber. A casting material is then poured into the chamberover the impression to create a model. A lid is subsequently placed overthe chamber. The chamber is opened and the mould can be removed afterthe specified time.

Examples of casting materials include auto polymerizing acrylic resin,thermoplastic resin, light-polymerized acrylic resins, polymerizingsilicone, polyether, plaster, epoxies, or a mixture of materials. Thecasting material is selected based on the uses of the cast. The materialshould be easy for cutting to obtain individual tooth model.Additionally, the material needs to be strong enough for the tooth modelto take the pressure in pressure form for producing a dental aligner.Details of making a dental aligner are disclosed in commonly assignedand above referenced U.S. patent application titled “Method andapparatus for manufacturing and constructing a dental aligner” byHuafeng Wen, filed Nov. 1, 2004, the content of which is incorporatedherein by reference.

FIG. 10 and FIG. 11 respectively illustrate exploded top and bottomperspective views casting chamber 1001 including a chamber body 1010, achamber lid 1002, and a chamber base 1003 for casting a physical toothmodel. Chamber body 1010 assembly includes a cavity 1020 and a mountingplate 1030 inside the chamber cavity 1020.

A negative impression of a patient's tooth or arch can be glued orfastened to the mounting plate 1030. At the bottom surface 1031 of theimpression mounting plate 1030, there are two precision alignment linersthat mate with two precision locating pins on the chamber cavity 1020bottom surface. The two precision locating pins and liners allow preciselocating of the impression repetitively. Furthermore, multiple throughholes 1033 through the bottom of the cast chamber to the cavity 1020provide access to the impression mount plate to assist the removal ofthe impression mounting plate 1030 from the cast chamber.

The chamber lid 1002 is mated precisely to the casting chamber body 1010by two precision locating liners 1015 on the chamber lid 1002 and twoprecision alignment pins 1055 on the casting chamber assembly topsurface. The two precision locating liners 1015 on the chamber lid 1002and the aligners 1022 on the chamber body 1010 also serve as positionreferences for measurement and machining. These features allowrepetitive cast of the teeth with precise locations of the teeth.

On the bottom of the casting chamber 1001, there are two additionalprecision alignment liners 1035. The two liners register with twoprecision locating pins on the casting chamber base sub-assembly, whichallows precise installation of cast chambers to the chamber base formeasurement and machining.

Chamber lid 1002 can include a variable spacer 1050 and a castingadaptor. The thickness of the variable spacer is determined by measuringthe height of the impression inside the casting chamber cavity 1020. Themaximum thickness of the spacer is used so that the distance of thecasting adaptor and the impression is minimum when the lid 1002 istightly placed on the casting chamber body 1010. To achieve the minimumdistance between the casting adaptor and the teeth, the adaptor can havea horse-shoe-shaped extrusion machined out of plastics or metal parts.

The casting adaptor is a machined part. Measurements of the specificteeth impression are used to calculate the required machine operations.There are multiple undersized holes on the adaptor to hold the metalpins tightly during the casting process. The locations and orientationsof the pins are calculated from measurements of the impression insidethe cavity 1020 of the chamber body 1010. In some cases, ahorse-shoe-shaped extrusion step is also machined based on specificmeasurement.

The casting chamber lid 1002 includes multiple threaded through holes1016 around the cavity 1020 of the casting chamber 1001. These holesserve as a lifting unit to overcome the large forces involved inde-molding. Metal bolts or screws are pushed through the threaded holesto lift the chamber lid 1002 and the cured mold out of the impression.

A plurality of through holes on the casting chamber lid 1002 allows thefastening of the chamber lid 1002 to the Chamber body 1010 during thecast and cure process. The chamber lid 1002 is fixed tightly to thecasting Chamber body 1010, maintaining the precision locations duringprocesses such as vibrating, elevated temperature cure process as wellas transportation during the cure process.

The casting chamber lid 1002 also has a slotted through window 1040.This window acts a view port as well as an overflow reservoir for theplastics liquid. The chamber lid 1002 also includes a handle 1028 foreasy carrying and handling of the chamber lid 1002. In anotherembodiment, the window allows UV light irradiation through the window toassist the polymerization and solidification of the casting material inthe casting chamber 1001. The cast material can be solidified by coolingor heating, irradiation by UV or IR light, or by microwave radiation.The cast material can comprise one or more crosslinking agents that cancause the polymerization and solidification of the cast material toproduce the physical tooth model.

Chamber base 1003 is normally fixed to a platform using the multiplethrough holes 1036. The platform can also host measurement devices. Thetwo precision locating pins on the chamber body 1010 with the twoprecision liners 1038 on the bottom of a chamber body 1010, thus producerepetitively precision mount of the casting chambers 1001 on to thechamber base 1003.

A feature of the disclosed casting system is the uses of precisionlocating pins and liners in the casting chamber 1001, the chamber lid1002 and the chamber base. Precision measurement and computer softwarecan also be used to produce the positions of the receiving features ofthe physical tooth model. The receiving features enable the physicaltooth mode to be mounted or attached to a physical base. The receivingfeatures can include a pin, a registration slot, a socket, a notch, aprotrusion, a hole, an interlocking mechanism, a jig, and a pluggable orattachable feature. The physical base as shown in FIGS. 2-9 includecomplimentary second features for receiving the first features to enablethe physical tooth models to be mounted to the physical base. Theprecise positions of the first features are used for determining thelocations of the second features in the physical base in fabricating thebase.

In accordance with the present system, the precision units in thecasting chamber design are also used in other manufacturing processessuch as 2D scanning, base plate machining, and bite setting measurement.2D scanning is a manufacturing process where an impression for apatient's teeth are measured for the positions and orientations of thesimulated “roots”—the metal pins. A measurement device such as adigitizer is mounted rigidly on a flat platform. Multiple pairs ofprecision locating pins on the platform can receive the mating precisionliners on the bottom of the casting chamber 1001. The locating pinspositions relative to the measurement device are precisely machined andmeasured, providing position references for the measurements. Themeasurement device must have the capabilities of measuring 5-degree offreedoms at each reading in order to provide accurate and efficientmeasurements.

After a casting chamber 1001 is placed on top of this measurementplatform, the chamber can be fixed or clamped down tightly withfasteners through the mounting holes on the casting chamber 1001. Themeasurement device such as a digitizer is first calibrated against theparticular chamber, by measuring the locations of two precision locatingpins at the top of the surface. After calibration, the locations andorientations of each tooth are measured. More than two points for eachtooth are measured. The gingival shape is also measured. Othermeasurements include the height of the impression, etc. These positionsand orientation data is stored in a computer to be used for futuretreatment and manufacturing processes.

Bite setting positions of the upper teeth and lower teeth of a patientcan also be measured using references to the precision locating linerson the casting chamber lid. After both the lower teeth and the upperteeth of a patient are cast, and de-molded. The two chamber lids withthe upper teeth and the lower teeth are set to their nature bite settingposition. Springs and universal joints can be used to hold the upper andlower teeth with chamber lids in the bite setting position. Ameasurement device is then used to measure the relationships between thepair of the precision locating liners on both chamber lids. With theassistance of known positions of the teeth to each chamber lids that aremeasured and calculated during the machining of the base plate, thenature bite position of the upper and lower teeth are then calculated.

Features that enable tooth models to be attached to a base (step 120)can be added to the casting material in the casting process.Registration points or pins can be added to each tooth before thecasting material is dried. Optionally, universal joints can be insertedat the top of the casting chamber 1001 using specially designed lids,which would hang the universal joints directly into the casting area foreach tooth.

Still in step 110, individual tooth models are next cut from the archpositive. One requirement for cutting is to obtain individual teeth insuch a manner that they can be joined again to form a tooth arch. Theseparation of individual teeth from the mould can be achieved using anumber of different cutting methods including laser cutting andmechanical sawing.

Separating the positive mould of the arch into tooth models may resultin the loss of the relative 3D coordinates of the individual toothmodels in an arch. Several methods are provided in step 120 for findingrelative position of the tooth models. In one embodiment, uniqueregistration features are added to each pair of tooth models before thepositive arch mould is separated. The separated tooth models can beassembled to form a physical dental arch model by matching tooth modelshaving the same unique registration marks.

The positive arch mould can also be digitized by a three-dimensionalscanning using a technique such as laser scanning, optical scanning,destructive scanning, CT scanning and Sound Wave Scanning. A physicaldigital arch model is therefore obtained. The physical digital archmodel is subsequently smoothened and segmented. Each segment can bephysically fabricated by CNC based manufacturing to obtain individualtooth models. The physical digital arch model tracks and stores thepositions of the individual tooth models. Unique registration marks canbe added to the digital tooth models that can be made into a physicalfeature in CNC base manufacturing.

Examples of CNC based manufacturing include CNC based milling,Stereolithography, Laminated Object Manufacturing, Selective LaserSintering, Fused Deposition Modeling, Solid Ground Curing, and 3D inkjet printing. Details of fabricating tooth models are disclosed incommonly assigned and above referenced U.S. patent application titled“Method and apparatus for manufacturing and constructing a physicaldental arch mode” by Huafeng Wen, filed Nov. 1, 2004, the content ofwhich is incorporated herein by reference.

In another embodiment, the separated tooth models are assembled bygeometry matching. The intact positive arch impression is first scannedto obtain a 3D physical digital arch model. Individual teeth are thenscanned to obtain digital tooth models for individual teeth. The digitaltooth models can be matched using rigid body transformations to match aphysical digital arch model. Due to complex shape of the arch,inter-proximal areas, root of the teeth and gingival areas may beignored in the geometry match. High precision is required for matchingfeatures such as cusps, points, crevasses, the front faces and backfaces of the teeth. Each tooth is sequentially matched to result inrigid body transformations corresponding to the tooth positions that canreconstruct an arch.

In another embodiment, the separated tooth models are assembled andregistered with the assistance of a 3D point picking devices. Thecoordinates of the tooth models are picked up by 3D point pickingdevices such as stylus or Microscribe devices before separation. Uniqueregistration marks can be added on each tooth model in an arch beforeseparation. The tooth models and the registration marks can be labeledby unique IDs. The tooth arch can later be assembled by identifyingtooth models having the same registration marks as were picked from theJaw. 3D point picking devices can be used to pick the same points againfor each tooth model to confirm the tooth coordinates.

The base is designed in step 130 to receive the tooth models. The baseand tooth models include complimentary features to allow them to beassembled together. The tooth model has a protruding structure attachedto it. The features at the base and tooth models can also include aregistration slot, a socket, a notch, a protrusion, a hole, aninterlocking mechanism, and a jig. The protruding structure can beobtained during the casting process or be created after casting by usinga CNC machine on each tooth. The positions of the receiving features inthe base are determined by either the initial positions of the teeth inan arch or the desired teeth positions during a treatment process (step140).

Before casting the arch from the impression, the base plate is takenthrough a CNC process to create the female structures for eachindividual tooth (step 150). Then the base is placed over the castingchamber in which the impression is already present and the chamber isfilled with epoxy. The epoxy gets filled up in the female structures andthe resulting mould has the male studs present with each tooth modelthat can be separated afterwards. FIG. 2 shows a tooth model 210 withmale stud 220 after mould separation. The base 230 comprises a femalefeature 240 that can receive the male stud 220 when the tooth model 210is assembled to the base 230.

Alternatively, as shown in FIG. 3, a tooth model 310 includes a femalesocket 315 that can be drilled by CNC based machining after casting andseparation. A male stud 320 that fits the female socket 315 can beattached to the tooth model 310 by for example, screwing, glueapplication, etc. The resulted tooth model 330 includes male stud 310that allows it to be attached to the base.

Male protrusion features over the tooth model can exist in a number ofarrangements. FIG. 4 shows a tooth model 410 having two pins 415sticking out and a base 420 having registration slots 425 adapted toreceive the two pins 415 to allow the tooth model 410 to be attached tothe base 420. FIG. 5 shows a tooth model 510 having one pins 515protruding out and a base 520 having a hole 525 adapted to receive thepin 515 to allow the tooth model 510 to be attached to the base 520. Ingeneral, the tooth model can include two or more pins wherein the basewill have complementary number of holes at the corresponding locationsfor each tooth model. The tooth model 610 can also include cone shapedstuds 620 as shown in FIG. 6. The studs can also take a combination ofconfigurations described above.

As shown FIG. 7, the studs protruding our of the tooth model 710 cantake different shapes 720 such as oval, rectangle, square, triangle,circle, semi-circle, each of which correspond to slots on the basehaving identical shapes that can be drilled using the CNC basedmachining. The asymmetrically shaped studs can help to define a uniqueorientation for the tooth model on the base.

FIG. 8A shows a base 800 having a plurality of sockets 810 and 820 forreceiving the studs of a plurality of tooth models. The positions of thesockets 810,820 are determined by either her initial teeth positions ina patient's arch or the teeth positions during the orthodontic treatmentprocess. The base 800 can be in the form of a plate as shown in FIG. 8,comprising a plurality of pairs of sockets 810,820. Each pair of sockets810,820 is adapted to receive two pins associated with a physical toothmodel. Each pair of sockets includes a socket 810 on the inside of thetooth arch model and a socket 820 on the outside of the tooth archmodel.

Another of a base 850 is shown in FIG. 8B. A plurality of pairs offemale sockets 860, 870 are provided in the base 850. Each pair of thesockets 860, 870 is formed in a surface 880 and is adapted to receive aphysical tooth model 890. The bottom portion of the physical tooth model890 includes a surface 895. The surface 895 comes to contact with thesurface 880 when the physical tooth model 890 is inserted into the base850, which assures the stability of the physical tooth model 890 overthe base 850.

A tooth model 900 compatible with the base 800 is shown in FIG. 9. Thetooth model 900 includes two pins 910 connected to its bottom portion.The two pins 910 can be plugged into a pair of sockets 810 and 820 onthe base 800. Thus each pair of sockets 810 and 820 uniquely defines thepositions of a tooth model. The orientation of the tooth model is alsouniquely defined if the two pins are labeled as inside and outside, orthe sockets and the pins are made asymmetric inside and outside. Ingeneral, each tooth model may include correspond to one or a pluralityof studs that are to be plugged into the corresponding number ofsockets. The male studs and the sockets may also take different shapesas described above.

A tooth arch model is obtained after the tooth models are assembled tothe base 800 (step 160). The base 800 can comprise a plurality ofconfigurations in the female sockets 810. Each of the configurations isadapted to receive the same physical tooth models to form a differentarrangement of at least a portion of a tooth arch model.

The base 800 can be fabricated by a system that includes a computerdevice adapted to store digital tooth models representing the physicaltooth models. As described above, the digital tooth model can beobtained by various scanning techniques. A computer processor can thengenerate a digital base model compatible with the digital tooth models.An apparatus fabricates the base using CNC based manufacturing inaccordance with the digital base model. The base fabricated is adaptedto receive the physical tooth models.

The physical tooth models can be labeled by a predetermined sequencethat define the positions of the physical tooth models on the base 800.The labels can include a barcode, a printed symbol, hand-written symbol,a Radio Frequency Identification (RFID). The female sockets 810 can alsobe labeled by the parallel sequence for the physical tooth models.

In one embodiment, tooth models can be separated and repaired after thebase. The tooth models can be removed, repaired or replaced, andre-assembled without the replacement of the whole arch model.

Common materials for the tooth models include polymers, urethane, epoxy,plastics, plaster, stone, clay, acrylic, metals, wood, paper, ceramics,and porcelain. The base can comprise a material such as polymers,urethane, epoxy, plastics, plaster, stone, clay, acrylic, metals, wood,paper, ceramics, porcelain, glass, and concrete.

The arch model can be used in different dental applications such asdental crown, dental bridge, aligner fabrication, biometrics, and teethwhitening. For aligner fabrication, for example, each stage of the teethtreatment may correspond a unique physical dental arch model. Alignerscan be fabricated using different physical dental arch models one at atime as the teeth movement progresses during the treatment. At eachstage of the treatment, the desirable teeth positions for the next stageare calculated. A physical dental arch model having modified teethpositions is fabricated using the process described above. A new aligneris made using the new physical dental arch model.

In accordance with the present system, each base is specific to an archconfiguration. There is no need for complex and costly mechanisms suchas micro-actuators for adjusting multiple degrees of freedom for eachtooth model. The described methods and system is simple to make and easyto use.

The described methods and system are also economic. Different stages ofthe arch model can share the same tooth models. The positions for thetooth models at each stage of the orthodontic treatment can be modeledusing orthodontic treatment software. Each stage of the arch model mayuse a separate base. Or alternatively, one base can be used in aplurality of stages of the arch models. The base may include a pluralityof sets of receptive positions for the tooth models. Each setcorresponds to one treatment stage. The tooth models can be reusedthrough the treatment process. Much of the cost of making multiple tootharch models in orthodontic treatment is therefore eliminated.

Although specific embodiments of the present system have beenillustrated in the accompanying drawings and described in the foregoingdetailed description, it will be understood that the system is notlimited to the particular embodiments described herein, but is capableof numerous rearrangements, modifications, and substitutions withoutdeparting from the scope of the system. The following claims areintended to encompass all such modifications.

1. A casting chamber to cast a physical tooth model representing apatient's tooth, comprising: a chamber body having a cavity adapted tohold a negative impression of the patient's tooth and to receive a castmaterial, wherein the negative impression and the chamber body areregistered by a registration unit; and a chamber lid configured to sealthe cast material in the casting chamber to permit the casting materialto solidify in the casting chamber and to form a physical tooth modelrepresenting the patient's tooth.
 2. The casting chamber of claim 1,wherein the chamber lid and the chamber body are registered by theregistration unit.
 3. The casting chamber of claim 2, wherein theregistration unit includes one or more of a registration pin, a locatingpin, an alignment hole, and a liner.
 4. The casting chamber of claim 1,further comprising a chamber base coupled to the chamber body.
 5. Thecasting chamber of claim 4, wherein the chamber base and the chamberbody are registered by a registration unit including one or more of aregistration pin, a locating pin, an alignment hole, and a liner.
 6. Thecasting chamber of claim 1, wherein the chamber body comprises one ormore chamber walls surrounding the cavity.
 7. The casting chamber ofclaim 6, wherein the chamber walls include one or more through-holes toenable the de-molding of the physical tooth model.
 8. The castingchamber of claim 1, further comprising a unit that is configured toassist the solidification of the casting material within the castingchamber.
 9. The casting chamber of claim 8, wherein the unit providesone or more of cooling, heating, emitting UV light, emitting IR light,and radiating microwave.
 10. The casting chamber of claim 1, furthercomprising a window in the chamber lid to permit the irradiation of UVlight or IR light through the window to the casting material.
 11. Acasting chamber for casting a physical tooth model representing apatient's tooth, comprising: a chamber body having chamber wallssurrounding a cavity, wherein the cavity is adapted to hold a negativeimpression of the patient's tooth and to receive a cast material and thenegative impression and the chamber body are registered by aregistration unit; and a chamber lid configured to seal the castmaterial in the casting chamber to permit the casting material tosolidify in the casting chamber thereby forming a physical tooth modelrepresenting the patient's tooth.
 12. The casting chamber of claim 11,wherein the chamber lid and the chamber body are registered by theregistration unit comprising one or more of a registration pin, alocating pin, an alignment hole, and a liner.
 13. The casting chamber ofclaim 1, further comprising a chamber base adapted to be held to thechamber body.
 14. The casting chamber of claim 13, wherein the chamberbase and the chamber body are registered by the registration unitincluding one or more of a registration pin, a locating pin, analignment hole, and a liner.
 15. A method for producing a physical toothmodel, comprising: receiving a negative impression of a patient's toothin a casting chamber; pouring a cast material over the negativeimpression of the patient's tooth; and solidifying the cast material toproduce the physical tooth model.
 16. The method of claim 15, whereinthe registration unit includes one or more of a registration pin, alocating pin, an alignment hole, and a liner.
 17. The method of claim15, further comprising sealing the casting chamber by a chamber lid topermit the solidification of the casting material.
 18. The method ofclaim 15, wherein the casting a material is selected from the groupconsisting of polymers, thermal elastic material, urethane, epoxy,plaster, clay, acrylic, latex, dental PVS, resin, metal, aluminum, ice,wax, and one or more crosslinking agents for polymerization.
 19. Themethod of claim 15, further comprising cooling or heating the castmaterial to cause the solidification of the cast material to produce thephysical tooth model.
 20. The method of claim 15, further comprisingirradiating the cast material with UV light or IR light to cause thesolidification of the cast material to produce the physical tooth model.